Method of and means for reducing the effects of undesired oscillations



D. G. M CAA Oct. 17, 1933.

METHOD OF AND MEANS FOR REDUCING THE EFFECTS OF UNDESIRED OSCILLATICNS Filed Oct. 29, 1930 3 Sheets-Sheet 1 IMM Oct. 17, 1933. D, MccAA 1,931,445

METHOD OF AND MEANS FORREDUCING THE EFFECTS OF unmasmzn OSCILLATIONS Filed Oct. 29, 1930 ssneets-sneet 2 D. G. MCCAA Oct. 17, 1933.

METHOD OF AND MEANS FOR REDUCING THE EFFECTS OF UNDESIRED OSCILLATIONS Filed Oct. 29, 1930 3 Sheets-Sheet 3 Patented Oct. 17, 1933 UNITED STATES METHOD OF AND MEANS FOR REDUCING THE EFFECTS OF UNDESIRED OSCILLA- TION S 1 David G. McCaa, Philadelphia, Pa. H Application October 29, 1930. SerialNo. 492,055v 1 4 Claims. (Cl. 250-20) J This invention relates to methods and means for separating desired oscillations from undesired oscillations according to their amplitudes regardless of their frequencies and particularly refers 5 to methods of substantially. reducing the effects of the undesired oscillations on the desired oscillations to a minimum. The invention is a modification of the methods described and claimed in my co-pending application, Serial No. 74,087, filed 110 December 8, 1925 which has become Patent No.

1,814,051, granted July 14, 1931 and is a continuation in part thereof.

One object of the invention is to separatethe desired and undesired oscillations into components, subject said components to a uni-directional electro-motive force of constant magnitude and substantially equal to'the peak voltage of the desired oscillations, thereby multiplying the frequency of the undesired oscillations, and caus- ;2 ing said components of multiplied frequency oscillations to oppose each other while the components of the desired oscillations are caused to add to each other, thereby increasing their amplitudes to affect a translating device.

A further object is to divide said desired and undesired oscillations into a pair of components, and again dividing each component into additional componets multiplying the frequency of both the desired and undesired oscillations in the 1430 last-mentioned components, and causing the components of the multiplied frequency to oppose each other-so as to have substantially no effect on a translating device and adding a uni-directional electro-motive force tothe other of said components whereby the components of the desired oscillations are'caused'to combine cumulatively to affect translating device and the components of the undesired oscillations are caused to substantially oppose'the other, thereby caus- 40 ing said translating device to be substantially unaffected by the undesired oscillations.

Other objects will appear hereinafter. The organization and operation of the circuits of my invention will be understood from the draw- 45 ings in which:

Fig. 1 is a schematic wiring diagram of the circuits of my invention, as applied to audio frequencies;

operation of my invention;

Fig. 4 is a diagram similar to that of Fig; 1

multiplying transformers are used;

Figs. 2 and 3 are explanatory curves of the Fig. 6 is a further modification wherein rectiflers are used;

Figs. 7 and 8 are modifications wherein the in, vention is applied directly to the translating device; I

Figs. 9 and 10 are explanatory curves; and

Fig. 11 is a system embodying successive free quency multipliersand filters.

Referring to Fig.1, there are indicated, tw thermionic tubes V and V1, each comprising an 05. anode a and a hot filament orcathode f. Associated with the tubes are the magnetic field coils M and M1, which, when traversed by a current, vary the impedance between the anodes and oath: odesof the tubes, as well understood in the art. 7 v The coils are connected in parallel branches to one terminal of the source S. which represents a, source ofaudio frequency currentsof diiferent amplitudes and of different characteristics, the lesser amplitude representing the-desired signal oscillations while the greater'amplitude currents represent the undesired oscillations which may be atmospheric disturbances orany other electrical disturbances. The plate circuits of the tubes V and V1 are the primaries p and p1 and. a source of plate current B, the primaries p and in opposing each other in their efiect upon the secondary S, to which is connected the telephone instrument or any suitable sound reproducer. Between the terminal ofsource Sand the coils M and M1 areinserted sources of unidirectional elec tro-motive forces E and E1, the valuespf which may be varied by meansof the potentiometer resistances n. The source E has its positive termi-, nal connected to one end of the coil M, while the source E1 has the negative terminal connected to one endof the coil M1. The other terminals of the coils M and M1 are connected together and to the other terminal of the sources. The source S receives its energy from the output of the detector tube D which maybe 01 the usual three W electrode thermionic vacuum tube type which detectsthe radio frequency currents collected by the antenna circuit AG and tuned. by the condensers C and C1. Heterodyne reception maybe used if desired, in which case;alocal sourceof' alternating currentsH is-impressed on the input circuit to the detector tube D. I i

. The operation of the system of Fig. lmay be understood upon reference to Figs. ,2 and 3. In 105 Fig. 2 the curve m represents an alternating currentthrough the coil M and the curve m represents :thealternating current simultaneously existing in the coilM1. .The curve 1); shows the variation. of current, from the source B in the prino mary p for the current m in the coil M; and similarly the curve 11 represents the current from the source B through the primary 101 for the current 1m in the coil M1. As is apparent, the current impulses p and 171 are in phase and neutralize each other.

The-system of Fig. l is rendered suitable for differentiating between the low and high amplitude currents from the source S by recourse to the sources of electro-motive-force E and E1 connected in opposite senses with respect to the source S in the circuits of the coils M and M1, respectively.

As indicated in the right-hand portion of Fig. 2, there is shown a curve mm which is the resultant of the curve m and electro-motive-force E; The source E in effect shifts the curve m upwardly so that it varies periodically between positive maxima and zero. Similarly, the curve m3 shows the effect of the electro-motiveforce E1 upon the current fm, shifting it entirely below the zero whereby the current through the coil M1 varies from zero through successive negative maxima. The result upon the current through the primary p is indicated by the curve 112 and the effect upon the current through the primary n is indicated bythe curve 193. The curves p2 and 1);; show that the currents through the primaries p and p1 representative of the low amplitude current representing the signal now are in effect dephased 180 degrees with respect to each other and, therefore, actcumulatively upon the secondary S, and, accordingly, the desired low amplitude signal-representing current affects the instrument T. Si-

multaneously, however, the interfering current of large amplitude has but slight effect upon the secondary S. Asindicated in Fig. 3, the halves of the interfering current of large amplitude are represented by the ecurves m4 and ms passing re spectively through the coils M and M1. The feeble lectro-motive-force Eassists the current m4 slightly, yielding a current represented by the curve me, while simultaneously the electro-motive-force E1 slightly opposes the current represented by the curve m5, yielding a current represented by the curve m7. As indicated by the arrows in Fig. 3, there is, therefore, but a slight resultant of the interfering current induced in secondary S.

It is important to note that without sources E and E1, frequency doubling action occurs in primary windings P and P1 when either is used separately with an alternating current input, and the waves of doubled frequency balanced out 'in secondary'S. This will be clear from an inspection of the curves p and p1 of Fig. 2 and'the curves of Fig. 9 to be described later. When sources E and E1 are used, however, primaries P and P1 each transfer a single frequency to secondary S until the input exceeds the potentialof E and E1, when double frequency action commences. This will be apparent from an inspection of the curves of Fig. 3 and those of Fig. 10 described hereinafter.

In Fig. 4 is shown an arrangement similar to I Fig. 1 exceptthat the source of alternating currents which traverse the coils M and M1 is of radio frequency instead of audio frequency and the input of the detector tube is received from the coils p and p1. Theoperation of the systems ofboth figures is fundamentally the same, including the balanced frequency multiplying action.

In Fig. 5 is shown a system utilizing a pair of frequency multiplying transformers'T and T1 in balanced relation. The transformers comprise pairs of primary windings M, M and M1, Midisposed on outer cores A, C, A1, and C1 and secondary windings S and S1 disposed on cores B and and S1 and the primaries M and M1 are idnserted sources of uni-directional electro-motive-force E and E1, the values of which may be varied by means of potentiometer resistances T2. The sources E and E1 may be poled as indicated, provided the polarities of S and S1 are as indicated, on one half cycle. The secondaries S and S1 are connected so as to oppose each other. Magnetizing windings W and W1 are provided on cores Band B1 and are connected in series with a source of uni-directional current 132.

In operation, the sense of direction or polarity of the fluxes set up by coils M and M1 at any given instant is such that they add in series in each of the flux paths comprising-cores A and C, and A1 and C1. With equal fluxes set up by coils M and M1 the terminals of cores B and B1 are subjected to equal and opposite magnetic poles, so that no active flux exists in cores B and B1 and no electro-motive-forces are developed in secondaries S and S1. The coils W and W1 are used to establish a fixed flux in the cores and end pieces. Now it will be seen that on one-half cycle the fixed and alternating fluxes will add in cores A and A1 and oppose in cores C and C1, while on the next half cycle they will add in cores C and C1 and oppose in cores Aand A1. The result is that for every half cycle there appears in cores B and B1 a pulse in the same direction. The double fre quency currents set up in secondaries S and Si by these pulses neutralize each other. This will be evident from the curves of Fig. 2 which apply equally here.

With uni-directional electro-motive-forces E and E1 introduced, however, the low amplitude currents are dephased and act cumulatively, as

transformer T is provided having two pairs of.

primary windings M and M1 on a common core and secondary S. The coil pairsM and M1 are wound oppositely, as shown, and are respectively connected in parallel relation with secondaries S and S1 of a transformer which represents a source of audio frequency currents. The induced E. M. F.s of S and S1"are of polarities asshown in the drawings during one-half cycle. Pairs of rectifiers R, R and R1, R1 are connected in circuit with the primaries M and M1 to provide alternate paths through the coils on each half cycle. In circuit with the pairs of primaries are inserted sources of uni-directional electro-motive-force E and E1 and potentiometer resistors r2, poled as shown.

It will be apparent that on the first half cycle of current from S and S1, current will flow through upper coils of M and M1, thereby setting up opposing fluxes in the core. On the next half cycle, current will flow through lower coils M and M1, thereby setting up opposing fluxes.

- resent the forces acting on the armature.

.due to action of its associated rectifiers and the direction of the windings. With E and .E1 in circuit,'however, the low amplitude signal currents are dephased and act cumulatively as shown in Fig. 2, while the large amplitude currents practically neutralize each other, as shown in Fig. 3.

Other arrangements for producing the same result as those previously described are shown in Figs. 7 and 8, wherein the multiplication of frequency is produced in the sound reproducing device itself In Fig. '7, the coils M and M1 are the windings of non-polarized electro-magnet y and are wound so as to oppose each other in their effects on the non-polarized armatureR, which actuates a drive rod q of a sound reproducer O. The action of coils M and M1 on armature R may be readily understood by reference to Figs. 2 and 3. 1 In Fig. 2, the arrows inclimate the direction of the forces simultaneously acting upon armature R. It will be noted that when sources E and E1 are absent, the forces of attraction are of double frequency but of opposite phase and, therefore, have no effect on the armature. For each alternation of the current, coils M and M1 exert two pulls on the armature in opposite directions, each in a single direction. By introduction of sources E and E1, however, the low amplitude signal currents are dephased, as shown in Fig. 2, and coils M and M1 act cumulatively on armature R. Simultaneously, the large amplitude currents have but slight effect on the armature, since they cause coils M and M1 to exert substantially equal and' oppositev forces thereon, as indicated by the arrows in Fig. 3.

In Fig. 8 is shown a transformer having secondaries S and S1 which represents a source of audio frequency currents. .Permanent magnets T and T1 are disposed as shown and have mounted thereon armature R. and pole pieces A,;B, C, and D. The'armature actuates a drive rod q of a sound reproducer O. The pole pieces receive magnetic flux of similar sign and of equal strength from the permanent magnets. A pair of, coilsM are wound on pole pieces B and C, while a similar pair M1 are wound on pole pieces A and D. The coil pairs are connected respectively to secondaries S and S1. Sources of uni-directional electro-motive-force E and E1 are connected to the respective coil pairs.

Neglecting sources E and E1, coils M1 are so connected that on one-half cycle of current pole piece A has a flux set up therein that addsto the permanent flux from magnetT1, while pole piece D has a flux established in it that opposes the permanent flux from T1. Simultaneously, pole piece B has a flux set up therein by coil M that adds to the permanent flux from magnet T, while pole piece C has a flux that opposes the flux from T. As a result, the permanent flux is shifted out of C and D into A and B. On the next half cycle, these relations reverse and pole pieces C and D become the main flux path. The

result is then that on one-half cycle, pole pieces A and B exert equal and opposite stresses on armature R, while on the next half cycle, pole pieces C and D exert equal and opposite stresses on armature R. This will be more clear by reference to Fig. 2, wherein the arrows again rep- Either of the coilsystems M or M1 acting alone in connection with its magnet T or T1 constitutes a polarized frequency changer. With sources E and E in circuit, however, and with the polarities j of S and S1 as shown, the low amplitude signal currents are 'dephased as shown in Fig; 2,-the current in coils'M1' goingto zero when the=cur'- rent in coil M is a maximum and vice versa. The arrows'indicate the cumulative stresses on the armature. Pole pieces A and C act'cumulatively on the armature, while the flux in pole pieces B and D aids the action of A and C. The-large amplitude currents, however, continue to produce substantially equal and opposite effects on the armature R, asshown in Fig. It should be noted that in thesystems; of Figs. 5, 7 and 8, wherein magnetic fiux relations are relied upon, the same result maybe obtained by providing fluxbiases to dephase the flux insteadof using electro-motive-forces E ,and E1. In such case, adjustable constant fluxes wouldbe provided to bias the fluxes setup by currents from the audio frequency source. The curves of Figs. 2 and 3 are applicable to such a system but must be considered as flux curves. 1

Theoperation of the system of Figs. 1 and 4 may be explained in anothermanner by means of the graphs of Figs. 9 and 10. Fig. 9 is a diagram of the magneto-motive-forces in coils M and M1 plotted against the plate to filament'im pedances of the'tubes V and V1;, Thesecharacteristics'are plotted without the sources E and E1 being in the circuit. The'curve a represents the desired or signal oscillations while curve b represents the undesired oscillations which may 5 be atmospheric disturbances and whose amplitudeis many times greater than the signal" amplitude. It will be seen fromjthis diagram that the desired oscillations a producea plate current flow in the primary p1, which'is represented by the curve 111 which is a pulsating current of double the original frequency. A similar plate current represented by curve a is produced in the primary p, which is of equal amplitude and frequency but of opposite phase, These currents a1 and a2, therefore, neutralize eachother completely. The currents b, which are ofhigher amplitude, -produce plate currents b1 and b: which arealso'of the Isamefrequency aridamplitude'but opposing phase producing a zeroresulta-nt.

In Fig. 10 is illustrated the action which takes place when the biasing electro-motive-forces E and E1 are introduced into the circuits of the coils M and M1. The sources E and E1 are of a magnitude. equal to the peak potential of the desired oscillations and are arranged so that E 01fsets the'characteristic of the tube V from its normal position in the positive direction by an amount equal to the peak'voltage of the desired oscillations while the source E1 offsets the characteristic of tube V1 in the negative direction by the amount equal to'the peak potential of the signal currents. It will now be noted that the plate currents produced in coils in and p1 represented by curves an and va1 are of the same frequency as the signal current a and of the same ampli-- tude and phase, while the plate currents produced by the undesired oscillations b' are of opposite phase, as indicated by b1 and b2, and frewave but contains harmonics of the resultant signal wave as. The wave In maybe passed through a filter but a higher amplitude wave results. If this latter wave is again passed through,

a balanced frequency raising device and a filter, a lower amplitude wave will be obtained. This operation may be repeated until a Wave similar in shape and amplitude to the signal wave as is obtained. Since a wave of the shape of D3 represents greater energy than wave as, it is desirable to subject it to the repeated frequency raising and filtering operation.

Such a system is shown inFig. 11, wherein the output'of a radio receiverjis subjected to successive stages of balanced frequency raising -and filtering. The balanced frequency raisers may, of course, comprise any suitable device, such as any of those disclosed. Likewise, the filters may be of any suitable type. The balanced frequency raising operation may be considered a cutting off operation, since it really cuts the disturbance wave down to signal amplitude. Therefore, the process is one which comprises repeatedly cutting off and filtering the wave until the desired wave is obtained. 7

While I have shown specific embodiments of 'my invention for the purpose of description of its principles of construction and operation, it is apparent that various changes could be'made therein without departing from the scope of the invention. I desire, therefore, that only such limitations shall be imposed thereon as are indicated in the appended claims. a

I claim:

1. Means for reducing the effects of undesired oscillations on desired oscillations comprisinga source of said desired and undesired oscillations, means for dividing said oscillations into components, means comprisinga plurality of transformers for multiplying the frequency of the components of the undesired oscillations by an integral number, and means for causing said components of multiplied frequency to oppose each other whereby they are substantially reduced in their effects on a translating device.

2. Means for reducing the effects of undesired oscillationson desired oscillations comprising a source of said desired and undesired oscillations, means for dividing said oscillations into components, means comprising a plurality of rectifier devices for multiplying the frequency of the components of the undesired oscillations by an integral number, and means for causing said components of multiplied frequency to oppose each other whereby they are substantially reduced in their effects on a translating device.

3. A system for reducing the effects of undesired oscillations on desired oscillations comprising a source of said desired and undesired OSCiI-r lations, means for repeatedly multiplying the frequency of said undesired oscillations by an integral number and for causing them to oppose each other after each frequency multiplying operation whereby resultant waves are obtained after each frequency multiplying operation, and means for filtering said'waves after each frequency multiplying operation.

4. A method for reducing the effects of undesired oscillations on desired oscillations which comprises successively dividing said oscillations into components, multiplying'the frequency of the components of the undesired oscillations by an integral number, and causing said components of multiplied frequencyto oppose each other after each frequency multiplying operationwhereby a resultant wave is obtained after eachfrequency'multiplying operation, and filtering said Wave after each frequency multiplying operation. a

DAVID G. McCAA. 12: 

